Health disparities are high among Latinas. They are more likely to be overweight, diagnosed with diabetes, and physically inactive compared to their non-Hispanic White counterparts. Thus, interventions that target improving health access and ameliorating chronic diseases among Latinas are of high public health importance. Regular physical activity (PA) promotes physical and emotional well-being, yet PA interventions tailored for Latinas remain limited. Available data suggest that community-focused interventions produce improvements in physical activity (PA) and are well-received by Latinas especially when social and physical environments are considered (e.g., social support, safe walking areas, etc.). Research suggests that Latinos respond favorably to technological-based health interventions. Almost 90 percent of Latinos own a cellphone; 60 percent own a smartphone. Thus, health promotion interventions that can address Latinos' preferences regarding their physical and social environments while utilizing a preferred technology source (e.g., smartphone) could prove highly successful. One smartphone feature that offers great potential health promotion benefit is location- based services (LBS). LBS use geographic positioning to help users connect to their surrounding environment and to other users, thus providing them with real-time, user-specific information. This proposed project, Caminamos!, will develop a smartphone app for use with 18-45 year old Latinas that uses LBS to connect women within geographically proximal neighborhoods as a way to provide social support for increased walking behaviors. Specific aims are: (1) gather input and evaluative feedback from an Expert Advisory Board (EAB) to help plan and assess the feasibility of creating the app; (2) build connections and gather input from Latino community leaders to assist in the conceptual development of the app through a Community Advisory Board (CAB); (3) conduct an online survey of a national sample of Latinas on their smartphone usage for health promotion, and interest in social networking and LBS technology features; (4) conduct iterative focus groups with Latinas age 18-45 years to guide development of app content, design, and aesthetics to fully develop a functioning prototype; and (5) conduct usability testing with Latinas to test the app's accuracy to establish users' location and connect users through the Caminamos! system and users' use and satisfaction with the app. Few app-based health products are branded towards Latinas. Caminamos! will address this unmet need in the marketplace. It will be the first smartphone app that uses location-based social networking to promote PA, and the only app of its kind targeted to Latinas. It will also expand upon what is known to be successful in Latino exercise engagement while simultaneously addressing key barriers to exercise. Phase I outcomes will provide the necessary framework and data for developing a full-scale app to be tested in a randomized clinical trial. In Phase III, we plan to market Caminamos! directly to consumers in partnership with a company interested in expanding their brand outreach to a Latina population.